This proposal seeks funding for the United States based IBCSG Statistical Center, a resource which would contribute to International-U.S. collaboration in the following areas: . Access to the IBCSG clinical database of 9,000 breast cancer patients with up to 15 years follow-up. . Access to the ICCSG tissue bank database for 1200 patients with 7 years follow-up. . Collaboration in the development of the IBCSG research agenda. This resource will give an opportunity for NCI to significantly improve our understanding of prognosis and treatment of women with operable breast cancer. The number of randomized trial that can be conducted in the United States cannot answer all of the questions about this population of patients. Support of this proposal for an IBCSG-NCI partnership will result in important new information about the appropriate clinical use of combined chemoendocrine therapy. The long-range goal of the IBCSG is to find the best possible treatments for early breast cancer. The specific aims of this application comprise the major areas of research toward this goal. . To provide US-based statistical and data management collaboration for the design, conduct, analysis and reporting of IBCSG randomized clinical trials evaluating adjuvant therapies. . To enable access to our uniformly treated and followed population of patients with the potential for tissue collection at diagnosis and relapse. . To provide the interface for clinical data collaboration on correlative studies designed to identify and confirm the relationship between characteristics of breast cancer patients and/or of breast tumors and response to adjuvant therapies. . To enhance collaboration between the IBCSG and US cooperative groups in the area of Quality of life evaluation for patients with breast cancer. . To explore opportunities for targeted meta-analyses of IBCSG and US cooperative group databases.